Enhancement of isobutane/butene alkylation by aromatic-compound additives in strong Brønsted acid

The aromatic-compound additive in sulfuric acid (H 2 SO 4 ) was found to promote isobutane/butene alkylation significantly. The selectivity of isooctane (C 8 ) and the alkylate research octane number increased by 23.46% and 5.09, respectively, when thiophene was added to H 2 SO 4 , especially. The proportion of trimethylpentanes can be improved from 58.57% to 84.58%, and the ratio of trimethylpentanes to dimethylhexanes was doubled, compared with that in the presence of H 2 SO 4 alone. The improved performance in the presence of thiophene additive in H 2 SO 4 is attributed to the improvement in carbenium-ion stability and the acceleration of hydrogen proton release, because of the existence of electron-rich π-bond compounds, and the substitution of thiophene in the alpha site by the sulfonic group and isobutane/butene. Reaction parameters such as reaction temperature, reaction time, stirring speed, feed rate, and acid/hydrocarbon volumetric ratio were also investigated in detail. The synergetic mechanism of thiophene-H 2 SO 4 on isobutane/butene alkylation was also speculated.